1. Field of the Invention
This invention relates to a tracer control system, and more particulary to a tracer control system which automatically changes the clamp level by a predetermined value for each working to perform clamp tracing continuously from rough to finish machining.
2. Description of the Prior Art
In clamp tracing according to a conventional tracer control system, for example, as shown in FIG. 1, a limit switch LS is provided at the position of a certain depth D of a model MDL where clamp tracing is desired to effect (which position will hereinafter be referred to as a clamp level); when the limit switch LS is turned ON by the movement of the tracer head, a feed in the direction of depth of the model MDL is stopped and a stylus is moved horizontally without contacting the model MDL: and tracing is re-started from the position where the stylus moves into contact with the model MDL. Upon completing of one machining operation, the position of the limit switch is changed, for example, by a predetermined depth of cut .DELTA.D to a position LS', where the same clamp tracing as mentioned above takes place. By repeating such operation, the configuration of the model MDL is finally traced down to its bottom. Thus, since the conventional system calls for the limit switch, the reliability of the tracing operation is relatively low because of the mechanical operation of the limit switch, and since the position of the limit switch must be changed for each working operation, it is difficult to continue working operations from rough to finish machining without a break and the working time is long as a whole.